Elevon stick control



T. A. FEENEY ET AL ,660,383

ELEVON STICK CONTROL Nov. 24, 1953 Filed Feb. 21, 1949 2 Sheets-Sheet lINVENTORJ 74/044414. ft'flv') mama: a P/62CC lttornay Nov- 24, 1 T. A.FEENEY a'r AL ELEVON STICK CONTROL 2 Sheets-Sheet 2 Filed Feb. 21 1949$5 5m E38 w I. H mm mam r NM/ 0 m .p W H mu 4 Patented Nov. 24, 1953ELEVON STICK CONTROL Thomas A. Feeney, Los Angeles, and Wallace B.Pierce, Burbank, Calif., assignors to Northrop Aircraft, Inc.,Hawthorne, Calif., a corporation of California Application February 21,1949, Serial No. 77,592

4 Claims.

The present invention relates to airplane controls, and moreparticularly the invention relates to a stick control for airplaneelevons.

Some airplanes, particularly those airplanes of the all-wing or taillesstypes, utilize a control surface called an elevon, mounted as part ofthe trailing edge of each wing panel. Means are then provided so thatthe pilot can move these control surfaces simultaneously in the samedirection for elevation control of the airplane and simultaneously inopposite directions for lateral control of the airplane. Thus thefunctions of the elevators and the ailerons of conventional airplanesare combined, only two surfaces being necessary for the combinedfunctions.

It is however, highly desirable that the pilots control element be soconnected to the elevons that this element can be moved for elevationand lateral control of the airplane, in exactly the same manner as thepilots control element is moved in conventional airplanes utilizingseparate elevators and ailerons.

It is an object of the present invention to provide an elevon controlsystem wherein the pilots control element is a stick, and whereincontrol of the airplane is obtained by stick movements substantially thesame as employed for airplane controls in conventional airplanes havingboth elevators and ailerons connected to the stick.

It is another object of the invention to provide a simple and positivestick control for airplane elevons.

In some large airplanes, such as, for example, the U. S. A. F. bombers13-35 and 13-49, which are of the all-wing type, the elevons areentirely power operated in accordance with movements of the pilotscontrol element. In such powered systems, no significant force need beexerted by the pilot in handling the airplane, the movements of thepilots control element transmitting only forces having the nature ofsignals to operate the elevon motors. In such cases backlash in thesystem should be held to the minimum.

Furthermore, in such'large airplanes, both a pilots and copilots stickcontrol is required, with linkage therebetween. This linkage alsocontributes to the production of backlash.

It is still another object of the present invention to provide an elevoncontrol system having means included therein to minimize backlash in thesystem, even when dual pilots controls are installed.

It has not heretofore been thought practical to control an airplane aslarge as the U. S. A. F. bombers referred to above (210,000 lbs. grossweight) with a stick. However, the present invention makes a stickcontrol practical for airplanes of any size, particularly when thecontrol surfaces are full power operated. These and other advantages andobjects of the present invention will be more apparent from the ensuingdescription of the appended drawings, which show, partlydiagrammatically, an elevon control system embodying preferred forms ofthe invention.

In the drawings:

Figure 1 is a schematic perspective view of an all-wing airplane showingan elevon control system embodying the present invention.

Figure 2 is a perspective view, partly diagrammatic, showing a preferredembodiment of the present invention as used in the system of Figure 1.

Figure 3 is a perspective view of a spring assembly forming a part ofthe device of Figure 2.

Figure 4 is a side view, partly in section, of a modification of thepresent invention.

Figure 5 is a top view, partly in section, of the modification shown inFigure 4.

The general layout of an elevon control system embodying the presentinvention is shown in Fig ure 1, as utilized in an all-wing, propellerdriven airplane l. Centrally, a pilots stick assembly 2 and a copilotsstick assembly 3 are connected to move right and left hand cables s and5 respectively, these cables being connected to operate right and lefthand 1 pairs of hydraulic motors B and I respectively. Each pair ofhydraulic motors moves an elevon 8 positioned to swing vertically in thetrailing edge of the airplane when the airplane is level.

The elevons 8 are moved in the same direction for elevation control, andin the opposite direction for lateral control of the airplane. Themechanism for causing such movement is shown in Figures 2 and 3 whichwill next be referred to.

The system shown in Figure 2 includes the pilots control stick assembly2 and a copilots control stick assembly 3. As the stick assemblies aresubstantially alike, only the copilots assembly 3 will be described, thepilots assembly 2 being given the same numerals for the same parts.

A stationary support shaft in is provided mounted in brackets llattached to the airplane to extend laterally in the airplane at rightangles to the center line thereof. Mounted to rotate freely on shaft inis a long sleeve !2, and mounted to rotate freely on long sleeve 12 is ashort sleeve 14. Long sleeve 12 carries a rearwardly extending rightelevon bevel gear sector it and short sleeve l4 carries a rearwardlyextending left elevon bevel gear sector l5 near the inner end thereof. Ayoke block I! is positioned to rotate freely on long sleeve I2 betweenthe two gear sectors l5 and it -;It will thus be seen that long sleeveIt, ehsrt sleeve 14 and "yoke block at all rotate around a common axisAA i. e. the center line of shaft I0, and that this common axis is at aright angle to the center line of the airplane.

A stick yoke is mounted with yoke legs 21 fore and aft of yoke block Hto rotate with re spect to yoke block I! on an axis at light angles toand intersecting common axis A-A. Thus axis BB is parallel to the centerline of the airplane. A control stick 2? is ertenaea upwardly from stickyoke 20. On the rear leg of yoke 20 is positioned a ear plate 24 havinglatra lv extend n d vinss ar se tors 25 nd, 26 ormed s a par the eci- Di ingsear sector 25 and. 2&5v re be el sear sec ors nd m sh res ec ivelyw th d iven ear ctors i5 and +5- Thaouter nd o lon -s eeve it adiacentshaf bra ket U s p o ided with a riel-it. elev n lev r- 2 andthe adiaent end o sh rt, leeve 4 is p ovided with al trelevon leve 3c B tw n he.pi ts stick s embly 2. nd the oopilots stick assembly 3 is positioned acable drive assembly 35.

ab driv assemblyfii ompr se an out pull r sleev 36 atin on imie c ncenric p y t:3lat -pul y sle ve 3.5 rotatesi n assembl e r n 39 su portedby assemb y ra ket 40:30: 1 th airframe- 'A' .ght lev0n-pu11 y Hismounted on. one-end of inner shaft 31 and a left elevon pulley 42; ismounted-0 h -adia entrend oi outer sleeve 36- T e o h e d. o ter sleve-3 S; isxattached to a left elevon d ivecrankfl and the other nd ofinner shaft il attached to a right elevon dri-ve. crank 45, Drive-cranks4-4-and 45 are of inverted v shape, and have their "respectiveoppositeslegs Su stantially parallel tQ-the rig-ht and left, elevonlevers team 3.0 of the. pilots-andcopilotFs stick as emblies-"2; andqrespectively. The 'tWOglBES; of t e r t. e von drivecrankfi-areattached to the. r spect ve;righteievonleyers zest-path the pilot-3s andcopilots, stick assemblies 2 and 3, "by iehte ev ndrive1iQdS:41,-andthetwo IegSoetne left elevon drive crank #14 are connectedto the respective left elevon leversfijlbf both;-pilot?s= and fioll lsistiek assemblies -2 and 3 by ion; elevon drive -rods;4 9

The yoke blocks. 11 inbotl' the pilot*s.and-'corpilots stickassemblies 2and 3*carrysdownwardly extending backlash levers fiilsattached:respecti-vely tethqlower'sides of the yokesblocks, these levers beingconnected by a backlash. cable. 52!, which includes. a turnbuckle '52..

Each elevon pulleylil anacadrivesrour cables extending outwardly the"wing panels tothe control'surface motora fi or lasthe case may b'e.is"both sides of the sy's'temaiesyihmetricalyonly theLeFt-Sidewill-be'shown anddescribed Fig:-

area.

The left elevon pulley 42 when rotated drives two upper cables "5a andtwo lower cables 5b. These'cables are led to the wing panel's on cablepulleys *5'4. One upper cable teat me-he lower cable -5b terminate on'opposite ends of a valve leverss 'and-the dtherupp'randlowei'jcableflike wise terminate in "a siniiliar 'val'veflejvefr.As'twfo surface control -'mo'tors are used and bothi'notor systems arealike, only the connections of one of them will be described.

Valve lever 55 is preferably vertically mountedto be rotated by cables5a and 5b on a central pivot 55. Above pivot 58, and between pivot 56'and the attachment of upper cable 5a, a pin 51 is extended l'ateinlh'rtocarry an operating lever 59 freely rotatable on pin 51. The upper end ofoperating lever 59 is attached to a feed back rod 50 extendingrearwardly to enter the elevon 8' hinged to swing vertically on theairframe of the airplane, llvithin elevon 8, rod till s pivoted to theside of a hydraulic cylinder 6| which, at one end thereof is attached toan operating arm 62 of elevon 8.

The piston (not shown) inside hydraulic cylinder 3! is attached to apiston rod 64 extending forwardly to terminate in an attachment fitting65 to tie the rod to the airframe.

The lower-end of operating leversil-is connected to a valve operatingrod 66 extending rearwardly to enter a hydraulic valve 61. This valvewhich is mounted on the airframe is connected to a hydraulic pressureline 59 and a fluid return line 'lll. The valve 6'! controls theadmittance of hydraulic fluid under pressure to opposite .sides of thepiston in cylinder 61. The :movement of valve operating rod 66 causesthe elevon 'to be moved by the hydraulic motor described, and-theresultant movementof the elevon 8 and attached cylinder 6!, actingthrough feed-back rod 60 and valve operating lever 59 and valve rod 66causes the surface to stop at a position as determined by the amount ofcable movement. This type of full power surface-control is more fullydescribed in a prior application by one of us -(-Feeney-) Serial No.23,567, filed :AprilZ'Z, 1948 As it-is-apparent that no feel-back-tothepilot can be provided by the motor system above described, and thatthe only force required to be exerted by the pilot is that sunicienttooveroome friction in thesystemand to move valve operating rod 66 invalve 61, a synthetic feel is providedlior the stick.

For the elevator action of thestick, a force. producing assembly 15 isattached to the backlash leverfic of the copilots control stickassembly3-. This force prodncingassembly liconsists of a foroespringassembly 15ahaving a casing 11 attached to theai-rirame, and having a springirod l9emerging therefrom and attached to a rod arm filtmountecl' on a forcespring shaft Bl. Casing H contains a spring (not-shown) that iscompressed by movement of springrodfiElaway-from aneu-tralpositionin-either direction.

Shaft 8| also carries a connecting lever -82 extending downwardly tojoin a connection rod 84 extending forwardly to connect with-the lowerend of backlash lever 53 of the =copil'ots stick mechanism Shaft it!also carries a concave cam 8 5,-on which ridesacarn roller =86.=attachedto.=-a vertical cam lever -til-"about, midway between. a pivot eilfi-an :aaphraemwod:end 9.0 of this cam lever.

Thediaphragm rod end Bil-of cam lever 81. is attached to-a diaphragm rod-91 extending forw d jo i phra m e2 insideaof 'azpressure casing94bisected by diaphragm 92. Forward-of diaphragm=92, a diaphragm spring95 'urgesdiaphragm 92 rearwardly so. that roller 86- on cam lever '8"!will at all times, when the iorcespring assembly 15a is centering springrod 19, tend to s'eekthe lowest position of cam'85.

To provide a force varying in accordance :with airspeed, the front ofdiaphragm 92 is supplied with ram air through ram air duct 96 and therear of the diaphragm is connected to a source of static pressurethrough static air duct 91. Thus pressure developed by diaphragm 92acts, through roller 86 and cam 85 to center the stick. The stickcentering force will be a force due to the force spring assembly plus aforce derived from airspeed. This latter force, varying as it does withairspeed, provides the pilot with a stick force simulating theaerodynamic force acting on the elevons, when the stick is moved inelevation controlling directions.

The stick i centered for aileron action solely by spring action. Thecentering springs used for this purpose are positioned to act on thedrive cranks, 44 and 45 and are best shown in Figure 3.

Positioned between the right and left elevon drive cranks 44 and 45,mounted to rotate freely on inner shaft 31 is a spring block I havingleaf springs IOI attached to opposite sides thereof and extendingdownwardly to terminate adjacent the ends of the legs of cranks 44 and45, with one spring between the forelegs of the drive cranks, and theother spring between the aft legs of the drive cranks. The longestlevers I02 of the spring face each other.

Closely adjacent the end of each spring IOI, a roller I04 is extendedfrom each leg of the drive cranks 44 and 45 in a position so that theserollers contact the inner surfaces of the leaf springs, near the freeends thereof, with the rollers of the left elevon crank 44 positionedjust below the rollers of the right elevon crank 45.

The leaf springs IOI are flexed around roller fulcrum pins I05 that aremounted between fulcrum plates I06, one of these plates being attachedon each side of spring block I00 and ex-- tending below the block toplace the fulcrum pins I05 in contact with the outer leaves of the leafspring IOI slightly below the attachment of these leaves to the springblock.

While the stick assemblies described above have the driving gear sectorsrotatable about the longitudinal axis BB with the driven gear sectorsrotating. about the lateral axis A-A, the reciprocal of this arrangementis equally useful and is shown in Figures 4 and 5. Here the stick 22 ismounted on a laterally extending stick tube IIO which is freelyrotatable on a longitudinal shaft III journalled in a forward bearingII2. A sector tube I I4 is mounted to rotate on longitudinal shaft IIIto rotate in a rear bearing II5.

Sector tube II4 terminates short of stick tube H0 and carries alaterally extending arm H6 on which a right driven sector H1 is mounted.The left driven sector H9 is mounted on a left sector arm I20 extendedin the opposite direction to arm I I6, and carried by longitudinal shaftII I. Right and left driving sectors I2I and I22 are respectivelymounted on the opposite outer ends of stick tube I I0 to mesh with thedriven sectors. Cables 4 and 5 leading to the hydraulic motors in thewing panels are taken from quadrants I23 and I24 respectively, attachedto shaft III and tube II4 beyond rear bearing II 5.

In the operation of the system shown in Figures 1, 2, and 3, when thestick is moved forwardly. or rearwardly away from neutral by the pilotof the airplane, the two driving sectors 25 and 26 engage andsimultaneously rotate the driven sectors I5 and I6 in the samedirection. This rotation actuates both right and left cables 4 and. 5 tocause the hydraulic motors 6 and I to move the elevons upwardly ordownwardly together, thus providing elevation control for the airplane.

Force. spring assembly 15a provides a stick cefi tering forceirrespective of airspeed, being useful on the ground and at lowairspeeds. At higher speeds the stick centering force of the forcespring assembly 15a is augmented by the force developed by the airflowacting on diaphragm 92 in casing 94, because movement of the stick inelevation directions will move cam causing roller 86 to ride out ofneutral position, the force on diaphragm 92 tending to return the roller86 to the lowest cam position.

. When the stick is moved laterally for lateral control of the airplane,one driven sector I5, for example, is rotated in one direction, and theother driven gear sector I6 is rotated in the other direction. Thisaction causes the cables to be actuated to control the hydraulic motorsto move one elevon upwardly, and the other one downwardly, therebyproviding aileron action for lat eral control of the airplane.

Any combination of elevation and lateral movements made by the sticks 22will be faithfully reproduced by the elevons.

It will be noted that when the stick is moved. fore and aft only, thatdrive crank 44 and 45 move together, and merely rotate spring block: I00without flexing the leaf springs IOI. How-- ever, when the stick ismoved laterally, drivecranks 44 and 55 move in opposite directions, andone roller I04 on one drive crank and one roller on the other drivecrank will bear against leaf springs IOI and flex them outwardly. Theurge of the leaf springs I 0| under these conditions provides acentering force between the two drive cranks 44 and 45 and thus providesa lateral centering force for the stick.

The action of the stick assembly shown in Figures 4 and 5 is similar,except that the shaft I I I and sector tube I I4 are rotated in oppositedirec-.

tions for fore and aft movement of the stick. Cross connections of thecables 4 and 5 to the quadrants I23 and I24 will provide elevon movementin the same direction for longitudinal movement of the stick, and in theopposite direction for lateral movement of the stick. In this case, thespring block I00 is mounted between quadrants I23 and I24 with the leafsprings IOI extending upwardly to engage rollers I04 mounted on thequadrants.

Referring again to Figure 1, it will be noted that as the pilots andcopilots stick assemblies are separated by the drive crank and pulleyassembly 35, it might be possible for one of the pilots to move acontrol surface slightly without moving the other pilots stick, if therewere to be any appreciable backlash in the gears of the mechanism, andin the linkage between the pulleys and the gears. To prevent suchbacklash, the pilots yoke and the copilots yoke are tied togetherthrough the backlash levers 50 and backlash cable 5|. This cable, whentightened by turnbuckle 52, loads the driving and driven gears in bothmechanisms through linkage rods 41 and 49 and all backlash between theseassemblies and between these assemblies and pulleys M and 42 iscompletely eliminated in all positions of the sticks, without, however,imposing any substantial resistance to stick movement. This is becausethe load imposed by the backlash cable operates through a closed loopconsisting of one backlash lever 50, the gear sectors of one stickcontrol assembly, the rods 41 and 49 and cranks 44 and 45, elevon levers29 and 30, of both assem-e blies, the gear sectors of. theotherassembly, the

aIlel relationship against increasing elastic Number Name Date forcesfrom said spring members. 1,832,254 'Spanovic Nov. 17, 1931 THOMAS A.FEENEY. 1,869,326 Ludlow July 26, 1932 WALLACE B. PIERCE. 2,045,269Henderson June 23, 1936 5 2,358,919 Fonck Sept. 26, 1944 ReferencesCited in the file of this patent 7 575 Lemonier 10, 945 UNITED STATESPATENTS 2,389,274 Pearsall et a1. Nov. 20, 1945 Number Name Da 2,445,343Tyra July 20, 1948 te 1,348,548 De Dominicis et a1. Aug. 3, 1920 10

